Kelly criterion sports betting calculator

The formula depends on an edge estimate

At decimal 2.00 and an estimated 55% win probability, the full Kelly fraction is 10%. Applying half of that fraction to a $1,000 reference bankroll produces $50. All figures follow the supplied assumptions.

Probability error can change the answer

The formula treats the entered probability as correct. If the true probability is lower, the calculated fraction can be too large. A quoted price does not establish the required probability estimate.

One modeled bet is not a personal plan

This tool handles a single binary outcome with full loss on a miss. It does not account for correlated open positions, personal finances or spending limits. A non-positive modeled edge produces a zero allocation.

Sensitivity to a small probability error

At even-money decimal odds of 2.00, full Kelly simplifies to 2p−1. Changing the estimated chance from 55% to 52% changes the fraction from 10% to 4%. At 50% there is no modeled edge and the allocation is zero.

The worked-example buttons contrast a supplied positive edge with a break-even estimate. Fractional Kelly scales a model; it does not validate the probability or establish an affordable personal loss limit. See responsible play.

Compare full, half and quarter Kelly together

The result shows all three fractions using the same inputs, followed by a probability sensitivity table. At decimal 2.00, an estimated 55% win probability and $1,000 reference bankroll, the full, half and quarter amounts are $100, $50 and $25. At a 50% estimate all three are zero. The five-percentage-point scenarios are illustrative changes to your assumption, not statistical confidence limits.